By Chet Yarbrough
Time, as a fourth dimension, is a mystery that Professor Sean Carroll partly unravels in a lecture series titled Mysteries of Modern Physics. Carroll helps Physics’ dilettantes, like this essayist; broaden understanding of the mechanics of the universe; albeit at the cost of some confusion and a headache.
Carroll defines words that are commonly understood by Physics’ students and vaguely or not understood by everyone else. He defines time’s arrow, entropy, and the second law of thermodynamics. Each definition offers insight to the mystery of time.
Time’s arrow seems to say you cannot remember the future, and you cannot un-break an egg. Time is thought to “only” allow recall of the past and experience of the present. However, Carroll suggests our current acceptance of “only one direction for time” may be wrong. Carroll explains that a combination of physics’ laws would not be violated if the arrow of time changes direction. It may be possible to remember the future; also, quantum theory’s laws of probability suggest a chance for reversing events of a cracked egg.
Carroll offers an explanation of how current quantum theory of the micro-world may suggest times’ arrow is reversible; i.e. Carroll’s explanation revolves around an undiscovered unified-field-theory that combines classic Newton/Einstein’ physics with quantum theory.
Carroll explains that entropy is a law of nature that posits all organization of things and beings degenerates into disorder.
This disorder is magnified by the second law of thermodynamics that says disorder is compounded by increases in the sum of all entropies of a participating system. The example given by Carroll is the impossibility of a perfect transfer of energy by an engine designed to provide power. In all engine designs, even though energy is always conserved, power is lost because the second law of thermodynamics shows that some energy escapes (an added entropy) in the power production process.
Because of entropy and the second law of thermodynamics, the macro-world reinforces observational belief that the arrow of time only goes in one direction. Carroll raises the question of the big bang and a singular event that suggests a period of time when entropy is either reversed or static; i.e. a time when more order than disorder is created. It seems, when the big bang occurred, entropy became the disorder of the universe and times arrow appears to point in only one direction. But, Carroll asks, what is there in space before the big bang? Carroll suggests prior to the big bang, the laws of entropy did not apply.
The answer may lay in future discoveries about dark energy and dark matter, two elements that make up 70% of the known universe. A step in that journey was made at CERN with the discovery of Higgs-Boson, an element of dark matter that gives form to all that we see.
Time remains a mystery at the end of Carroll’s lectures. Travel to the future seems a possibility. Travel to the past seems a logical impossibility.
Carroll speculates on the idea of a multiverse caused by periodic reversals of the arrow of time; i.e. reversals which create new universes from new big bangs. There is much more in Carroll’s lectures that tickle synapses and light dendrites of a listener’s mind.